In a device (charged particle beam device) using a convergent charged particle beam (probe beam) such as a scanning electron microscope (SEM) and an ion beam processing device (Focused Ion Bear: FIB), a sample is scanned with the probe beam, so that an observation image or the sample is processed. A resolution or processing precision of the charged particle beam device is determined by a cross-section size (probe diameter) of the probe beam and in principle, when the cross-section size is small, the resolution or the processing precision can be increased.
Recently, the development of an aberration corrector for the charged particle beam device has been advanced and its practical application has been advanced. In the aberration corrector, a resultant obtained by stacking multi-pole lenses including magnetic poles or electrodes in multiple stages is used. Each stage applies a rotationally asymmetric electric field/magnetic field such as a 2-pole field, a 4-pole field, a 6-pole field, and a 8-pole field to the beam in a superposed manner and gives a counter aberration to the probe beam.
As a result, the aberration corrector can cancel various aberrations such as a spherical aberration and a chromatic aberration occurring in an objective lens of an optical system, a deflection lens, or the like. In addition, aberrations caused by the rotationally asymmetric field of the aberration corrector as a dominant factor, for example, a two-fold symmetric astigmatism, a three-fold symmetric astigmatism, a coma aberration, a four-fold symmetric astigmatism, a star aberration, and the like can be adjusted in the corrector.
In order to maximize device performance in a charged particle beam application device including the aberration corrector, by appropriately adjusting the aberration corrector including the aberrations occurring in the corrector, influences of all aberration components must be removed from the probe beam.
In the adjustment of the aberration corrector, since the number of power supplies of multi-poles constituting the corrector is large and the adjustment work is complicated, automation for quantifying the aberrations included in the optical system, calculating a feedback amount to cancel each aberration for each of the aberrations, and applying feedback to the device is attempted.
An example of an aberration evaluation method in the charged particle beam device including the aberration corrector is disclosed in PTL 1. PTL 1 discloses a method of measuring the aberrations from an SEM image. Thereby, an aberration coefficient representing the magnitude of each aberration can be evaluated.
PTL 2 discloses that, in a transmission electron microscope (TEM) and a scanning transmission electron microscope (STEM) mounted with a conventional aberration corrector, a correction target value is determined for each aberration with respect to each aberration coefficient using the Rayleigh's quarter-wave rule, for example, and while the aberration corrector is adjusted so that the aberration becomes the target value or less, a wavefront phase shift of an electron beam due to the aberration is observed by a transmission electron image called Ronchigram and an aberration correction amount is confirmed.
On the other hand, in the charged particle beam device such as the SEM, a method of determining an image resolution of the SEM by evaluating a sample image scanned with the probe beam is known.